Flying control for aircraft



Aug. 8, 1950 H. KNOWLER EIAL FLYING CONTROL FOR AIRCRAFT 6 Shoots-Sheet 1 Filed Nov. 29, 1947 Aug. 8, 1950 H. KNOWLER EI'AL FLYING CONTROL FOR AIRCRAFT 6 Sheets-Sheet 2 Filed Nov. 29, 1947 Aug. 8, 1950 H. KNOWLER ETAL FLYING CONTROL FOR AIRCRAFT 6 Sheets-Sheet 3 Filed Nov. 29, 1947 Aug. 8, 1950 H. KNOWLER ETAL FLYING CONTROL FOR AIRCRAFT 6 Sheets-Sheet 4 Filed Nov. 29, 1947 H. KNOWLER ETAL FLYING CONTROL FOR AIRCRAFT Aug. 8, 1950 Filed Nov. 29, 1947 6 Sheets-Sheet 5 Aug. 8, 1950 H. KNOWLER ETAL FLYING CONTROL FOR AIRCRAFT 6 Sheets-Sheet 6 Filed Nov. 29, 1947 I Ill/III Patented Aug. 8, 1950 UNITED STATES PATENT OFFICE FLYINGCONTIROL FOR AIRCRAFT Henry Knowler, Ryde, andFrank Henry'Robertson, Carisbrooke, Isle of Wight, England, assignorsto Saunders-Roe Limited, East Cowes, Isle of Wight, England Application November 29, 1947,Serial No.

In Great Britain October 7, 1946 ,.The object ofthis inventionis to provide for power operation of the controlsurfaces of an aircraft. l i i l The invention provides, in an aircraft,,a power operated flying control system, comprising in combination with a pilots control member and a control surface to be operated thereby,;;a pair of powerunits linked to the pilots control memberand each arranged, on displacement of the control member, to execute a movement corresponding in amount and direction to the movement of the control member, a torque shaft,a differential gear coupling the power units to the torque shaft, an irreversiblemechanical driving gear for imparting movement from the torque shaft to the control surface, and means for preventing, reverse rotation of either power unit, should it fail; by the other power unit.

By virtue of the provision of a pair of power units driving the torque shaft through a differential gear, the system is safeguarded against failure to: the extent that, should either power unit fail, the other can continue to operatethe, control surface through the agency of the differw ential gear. A degree, of irreversibility is provided, either in the power units themselves or in the drivesbetween the power units andthe differential gear, so that the failed power unit will not be driven in reverse by the other and still ope ailing powerunit. l a

The irreversible drive between thetorque shaft and the controlsurface ensures that loads on the control surface will not be transmitted back through the system, sointroducing flexibility and the possibility of flutter in thelcontrol surface. By this means the mass balancing of the surface whichis at ated. i

Among other advantages of the arrangement according to the invention, no parking lock is required for the control surface, no mass balanc ing of the control surface is needed, no power is required to hold the control surface against the aerodynamicload, and no direct structural conn'ection is required between two or more parts of a controlsurface. Thus in thecasejof an elevator, the two parts thereof which are located on opposite sidesof the fin canbe operatedsimul taneously and insynchronism, by a single power operated irreversible mechanical drive,and a substantial weight can besavecl by the elimination of any structural connection between the two parts.

In the case of an aircraft fitted with a pressure cabin it is preferred to, dispose the power units within the pressurecabin. The power units can present foundnecessary, is obviiaeiaims. (01. 244-45) be operated directly by the pilots control memher. I In the; case of large aircraft, however, in which the pilot's cockpit is located at some distance from the end of the cabin, it is preferred to dispose the power units at the end of the cabin nearest the control surface, and to operate them gear boxes It, H5

by master and slave units from the control column, these comprising a transmitter connected to thecontrol member and a receiver connected to the power unit, the receiver following the movement imparted to the transmitter.

One specific embodiment of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of an aircraft showing the pilots controls and the power units for operating the various control surfaces,

Fig. ,2 is a diagram tion of the elevator,

Fig. 3 is a diagram showing a modified arrangement of the system shown in Fig. 2,

Fig. 4 is a side elevation, partly in section, of

one of the power units and the differential gear,

of the differential gear,

units removed,

Considering first of all Fig. 2, foreand aft= movement ofthe pilots control column H3 is effective, through a chain drive i i, to rotate a shaft 12 and thence, through chain drives [3, i l and to effect corresponding adjustment of a pair of electrical transmitters it, H6 of the Selsyn type. throughchain drive I], differential gear I 5 and chain drive 19 ha feel generator 26, which may be of the hydraulic plication Serial No. type described in 790,774, now U. S. May 23, 1950. A

788,868 or of the mechanical U. S. application Serial No.

trimmer 2i is connected to the planetcarrier of the differential gear l8 by a cable 2 2, and 23 is an automatic pilot.

The elevator 24 is operated by twin power units 25 is constituted by a con- "stantly running constant speed electric motor 26,

25, I25. Power unit showing the power operapartly in section, of one Coupled to the shaft I2,

type described in U'. S. an

Patent No. 2,508,883, issued on a variable delivery hydraulic pump 21 driven by the motor 25 and a hydraulic motor 28 driven by the pump 27, The pump 2? has a control lever or the like by which its delivery can be adjusted to correspond in direction and extent to the movement imparted to the control column I0. Normally the pump 27 is not delivering fluid. When, however, the control column is moved an electrical receiver 29 of the Selsyn type is positioned by the transmitter I5. and effects appropriate adjustment of the control lever of the pump The power unit I25 is of identical construction to power unit 25, the individual parts thereof being identified by corresponding numbers, prefaced by the digit I.

The hydraulic motors 28, I28 drive the sun wheels 55, ltd of a differential gear SI, from which, as explained later in more detail, movement is imparted to a torque shaft 32 for operating the elevator 25. The control levers of the pumps 2i, l2! are returned to neutral position, likewise as explained later in more detail, by means of follow-up gears 53, I33.

The power units 25, I25 will not be described in detail because they are of known construction. Each power unit constitutes an electro-hydraulic torque converter, the constant-speed variabl tor ue output of the electric motor being converted into a variable speed delivery and the speed of the hydraulic motor being determined by the speed at which the control member of the pump is moved by the pilot away from its neutral position. The power units thus give control not only of the position but of the rate or movement of the associated control surfaces, which is a necessar requirement in the case of the rudder, ele vator andailerons. Each of the hydraulic motors 28, I28 embodies a lock of the kind shown in Fig. '7. Slidably but non-rotatably mounted on the shaft 90 of the hydraulic motor is a piston 94. a pin 9i fixed to the shaft engaging a slot 98 in the piston. The piston 9! is normally held against a spring 53 by hydraulic pressure admitted through an inlet 52, in the position shown in Fig.

'7. In the event of failure of the hydraulic pres-- sure, however, the spring 93 will move the piston 9 I to the left to engage teeth 54 thereon with teeth 95 on a fixed member 95, so looking the shaft 90 against rotation. When either of the power units fails, it is thus locked against reverse rotation, through the differential gear 3I, by the other power unit, so that the other power unit will be effective to operate the elevator. As an alternative to providing locking devices in the power units, an irreversible drive could be introduced between each power unit and the differential gear 3I, so as to prevent reverse rotation of a failed power unit by the other power unit, Such an arrangement is shown in Fig. 8. Here the shafts 9,1), I90 05 the hydraulic motors 28, I28 drive the sun wheels 35, I of the differential gear through irreversible spiral drives 99, I99. The follow-up gear is not shown in Fig. 8, but this may be of similar construction to that shown in Fig. 2,.

Movement of the control column Ill actuates an electrical transmitter 34 of the Dessyn type to effect appropriate positioning or a pointer 35 on a scale 36 visible to the pilot. Pointer 35. thus shows the selected position of the elevator. Mo.ve-. ment of the elevator 24 actuates a second Dessyn transmitter 31 to position another pointer 38, to show the actual position of the elevator. When the apparatus is working Properly, Pointers 35,

4 38, which move on coaxial pivots, are in alignment on the scale.

When switches 39 are moved to on position from the "01? position shown in Fig. 2, relays 40 are energised from a power supply line I46 which serves also to supply power to the Dessyn transmitters 34, 31, thereby causing contacts 4| to close to connect the motors 26, I26 to a power supply line 42 and start the motors, and causing contacts 43 to close to connect the transmitters I6, H6 and receivers 29, I29 to a powe supply line 44.

The power units 25, I25 are located near the rear wall I I4 of the pressure cabin of the aircraft, through which the torque shaft 32 extends rearwardly, a suitable seal 45 preventing escape of air from the pressure cabin. The torque shaft 32 drives, through bevel gears 41 a pair of cross shafts 4-5 associated respectively with the port and starboard halves of the elevator 24, each of which is divided into two sections as shown. Each cross shaft 46 is supported in self-aligning bearings, indicated at 48, and drives, through a worm drive 49, a screw jack 50 associated with each section of the elevator.

Fig. 1 shows the layout of the flying controls for the elevator 24, rudder 5| and ailerons 52, the transmitter units being omitted for the sake of clarity. Fore and aft movement of the control column I0 effects remote operation of duplicated power units 25, I25 as already described, to actuate the elevator 24 through the torque shaft 32, which passes out of the pressure cabin through the seal 45. Lateral movement of the control column operates in precisely similar fashion, duplicated power units 225, 325 acting through a difierential gear 23! on torque shafts I32, which pass out from the pressure cabin through seals I45, and operate the ailerons 52 through screw jacks I50. In precisely similar fashion, movement of the rudder bar 53 effects remote operation of duplicated power units 425, 525 which drive a torque shaft 232 through a differential gear 23I. The torque shaft 232, which leaves the pressure cabin through a seal 245, actuates the rudder 5| through screw jacks 250.

Turning now to Figs. 4 and 5, the planet carrier 54 of the dififerential gear 3I carries a gear wheel 55 which meshes with a gear wheel 56 fixed to the torque shaft 32. As'the sun wheels 3|], I30 are rotated in same direction by their respcctive power units, the planet carrie" 54 will be continuously rotated to drive the torque shaft 32.

Associated with each power unit is a secondary differential gear 57 (Fig. 4).. The receiver unit 28 serves to drive the planet carrier 58 of the secondary differential gearthrough gears 59, 60, thereby, through sun wheel BI and pinion 62, adjusting a rack 53 coupled to the control lever (not shown) of the pump 28 to adjust the control lever appropriately to the setting imparted to the control column I5. As shown in Fig. 5, the gear wheel 55 drives, through gearing indicated generally by the reference 64, a pair of followup S f s "3 ociated one with each power unit. As shown in Fig. 4, follow-up shaft serves to drive the sun wheel 6.5 of differential gear 51, to turn sun wheel 5| in the direction reverse to that in which it was turned by the-receiver 29,, thereby causing rack 63 to return the control lever of the pump 21 to neutral position when the elevator has moved to the position selected by the control column.

The differential gear 3I is provided with extractor locks, by means of which, when either power unit is removed for inspection or replacement, the associated suri wheel is locked against rotation. As shown in Fig. 5, the motors28, I28

urged outwardly by springs 69. Normally, i. e.

when the power units are in position, the clutch coupling members loare held in against their springs 69 as shown atthe left hand side of Fig. 5. When however a power unit is removed, as shown at the right hand side of Fig.5, the spring 69 can move the coupling member "I outwards to bring a pinion 1| carried thereby into mesh with a fixed pinion 72, thereby locking the associated sun wheel against rotation, so that the remaining power unit can continue to-drivethe torqueshaft. l P i As a safeguard against jack seizure'feach screw jack is provided with a shear key, as shown in Fig. 6. As shown in Fig. 2, the ailerons'andrudder are divided into at least three sections each driven by an individual screw jack: Should any jack seize, and sufficient torque is applied to the shaft driving it, its shearkey will fail, freeing the shaft to enable it to continue to operate thejacks associated with the other sections of the control surface. As the shearing torque is shared between the shear keys of the jacks associated with the other sections, these will not fail. The elevator is divided into four sections, and the shearing torque applied to the shear key of i any of the associated jacks will be shared among the shear keys of the remaining three, being transmitted thereto through the cross shafts 46 and bevel gears 47.

Turning now to Fig. 6, each screw jack comprises a housing 13 mounted in trunnion bearings l4, and containing a worm wheel "15, meshing with the worm 49 on the cross shaft 45, and constituting a nut for imparting movement to a screwed shaft 16 for operating the control surface. The worm 49 is connected to the shaft 46 by a shear key 11 held in position by a split ring 18. If the shear key 11 fails, due to seizure of the jack, the shaft '46 can thereafter rotate free ly in the worm 49. l

As shown in Fig. 3, in the case of the elevator,

an additional safety mechanism may be provided for allowing the elevator to be returned to central position in the event of failure of both power units. To this end, an additional differential gear 19 is interposed in the torque shaft 32 between the motor driven differential gear 3| and the rear wall H4 of the pressure cabin, the sun wheels so of this second difierential gear being secured to the two parts of the torque shaft. Ifhe planet carrier BI is irreversibly geared, by a worm drive 82, to a normally inoperative auxiliary electric motor (not shown), so that the second differential gear normally operates merely, to reverse the direction of drive of the torque shaft, By operating a two-Way emergency switch, however, the pilot can cause the auxiliary electric motor to operate in forward or reverse direction to move the elevator accordingly.

What we claim as our invention and desire to secure by Letters Patent is: l

1. In an aircraft, the combination, witha pilots control member and a control surface to be operated thereby, of a torque shaft, an irreversible mechanical driving gear located adjacent the control surface for imparting movement from the torque shaft to the control surface, a pair of variable speed power units, a differentialgear amm coupling the power units to the torqueshaft, connections between the pilots control member and the power units for rendering the power units operative, on movement of the pilots control member, to move the control surface in a direc tion and at a rate determined by the movement of the pilots control member, means for termi nating operation of the power units on arrival of the control surface .at a position selected bythe movement of the control member, and means for preventing reverse rotation of either power unit, should it fail, by the other power unit. 1

2. In an aircraft, the combination, with a pi lots control member and a control surface to be operated thereby, of a torque shaft, an irreversible mechanical driving gear located adjacent the control surface for imparting movement from the torque shaft to the control surface, a pair of electro hydraulic torque converters, a differential. gear coupling the torque converters to the torqueshaft, connections between the pilots control: member and the torque converters for rendering the torque converters operative, on movement of the control member, to move the control surface in a direction and at a rate determined by th'e movement of the pilots control member, means for terminating operation of the power units on arrival of the control surface at a position se'- lected by the movement of the control member, and means for preventing reverse rotation of i either torque converter, should it fail, by the other torque converter.

3. In an aircraft, the combination, with a pilots control member and a control surface to be operated thereby, of a torque shaft, an irreversi ble mechanical driving gear located adjacent the control surface for imparting movement from the torque shaft to the control surface, a pair of variable speed power units each comprising a constantly running electric motor, a hydraulicpumpj, having a variable and reversible delivery, driven by the electric motor, a hydraulic motor driven by the pump, a differential gear transmitting the drive from the two hydraulic motors to the torque shaft, a connection between the pilots control member and each hydraulic pump for causing the pumpfon movement of said control memberjto drive its associated motor in a direction and at a speed corresponding to the direction and. speedof movement of said control member, a follow-up gear between the differential gear and the pumps for terminating delivery of the pumps whenrthe control surface has assumed a position selected by the control member, and means for preventing reverse rotation of either power unit, should, it fail, by the other power unit. i 4. In an aircraft, the combination claimed in claim 3, wherein each power unit includes a lock normally held in free position by the hydraulic pressure and a spring for moving the lock into position to lock the hydraulic motor of that power unit against rotation in the event of failure of hydraulic pressure in that unit. l

5. In an aircraft, the combination, with a pilots control member and a control surface to be operated thereby, of a torque shaft, an irreversi ble mechanical driving gear located adjacent the control surface for imparting movement fromthe torque shaft to the control surface, a pair of variable speed power units each comprising eonstantly running electric motor, a hydraulic pump, having a variable and reversible delivery, driven by the electric motor, a hydraulic motor driven by the pump, a differential gear transmitting the drive from the two hydraulic notors to the torque shaft, a master and slave unit interposed between the pilots control member and each power unit, each master and slave unit comprising a transmitter connected to the control member and a receiver connected to the hydraulic pump of the associated power unit and operative, on movement, of the control member, to cause the pump to drive its associated motor in a direction and at a speed correspondin to the direction and speed of movement of said control member, a follow-up gear between the differential gear and the pumps for terminating delivery of the pumps When the control surface has assumed a position selected by the control member, and means for preventing reverse rotation of either power unit, should it fail, by the other power unit.

, 6. In an aircraft, the combination claimed in claim 5, wherein the follow-up gear comprises a differential gear having a planet carrier and a pair of sun wheels, means controlled by the receiver of the associated master and slave unit for movingthe planet carrier in relation to the sun wheels, a connection between one of the sun wheels and a member for controlling the delivery of the associated hydraulic pump, and a connection between the other sun wheel and the differential gear driving the torque shaft.

7. In an aircraft, the combination, with a pilots control member and a control surface to be operated thereby, of a pair of variable speed power units controlled by the pilots control member and operative, on movement of the control member, to move the control surface to a position and at a rate determined by the movement of said control member, a torque shaft, a differential gear for imparting movement to the torque shaft from the two power units, means for preventing reverse rotation of either power unit, should it fail, by the other power unit, and at least one screw jack located close to the control surface for imparting movement thereto from the torque shaft.

'8. In an aircraft, the combination claimed in claim 7, wherein the control surface is divided into at least three sections, and comprising a drive shaft driven from the torque shaft and extending parallel to the hinge axis of the control surface, an individual screw jack for imparting movement to each section of the control surface from the drive shaft, and a shear key associated with each screw jack, said shear key being adapted to fracture, in the event of seizure of the screw jack, to allow of continued rotation of the torque shaft and drive shaft.

9. In an aircraft having a pressure cabin, the

combination with a pilots control member and a control surface to be operated thereby, of a pair of variable speed power units located within the pressure cabin, said power units bein controlled by'the pilots control member and operative, on movement of the control member, to move the control surface to a position and at a rate determined by the movement of said control member, a torque shaft extending out of the pressure cabin .and towards the control surface, a differential :gear within the pressure cabin for imparting :movement to the torque shaft from the two power 'units, means for preventing reverse rotation of either power unit, should it fail, by the other 'power unit, and an irreversible mechanical driviing gear close to the control surface for impart- .ing movement thereto from the torque shaft.

10. 'In an aircraft, the combination, with a pilots control member and a control surface to Tbe'operated thereby, of a torque shaft, an irrer 8 versible mechanical driving gear located adjacent the control surface for imparting movement from the torque. shaft to the control surface, a pair of variable speed power units, a differential gear coupling the power units to the torque shaft, said differential gear comprising a planet carrier geared to the torque shaft, a pair of sun wheels each mounted on a shaft adapted to be clutched to one of the power units when said power unit is in position to drive said differential gear, a lock associated with each of said shafts which is held disengaged when the associated power unit is so positioned, anda spring associated with each lock for moving the same to lock the shaft of the associated sun wheel against rotation on removal of the associated power unit from position to drive said differential gear, connections between the pilots control member and the power units for rendering the power units operative, on movement of the pilots control member, to move the control surface in a direction and at a rate determined by the movement of the pilots control member, means for terminating operation of the power units on arrival Of the control surface at a position selected by the movement of the control member, and means for preventing reverse rotation of either power unit, should it fail, by the other power unit.

11. In an aircraft, the combination, with a pilots control member and an elevator to be operated thereby, of a two-section torque shaft, an irreversible mechanical driving gear located adjacent the elevator for imparting movement from the torque shaft to the elevator, a pair of variable speed power units, a differential gear coupling the power units to the torque shaft, connections between the pilots control member and the power units for rendering the power units operative, on movement of the pilots control member, to move the elevator in a. direction and at a rate determined by the direction and rate of movement of the pilots control member, means for terminating operation of the power units on arrival of the elevator at a position selected by the movement of the control member, means for preventing reverse rotation of either power unit, should it fail, bythe other power'unit, av subsidiar differential gear interposed between the two sections of the torque shaft, said subsidiary differential gear comprising a pair of sun wheels each coupled to one section of the torque shaft, and a planet carrier, an electric motor, and an irreversible drive between said electric motor and the planet carrier of said second differential gear, said electric motor permitting of emergency operation of the elevator in the event of failure of both power units.

12. In an aircraft, the combination, with a pilots control member and a control surface to be operated thereby, of a torque shaft, an irreversible mechanical driving gear located adjacent the control surfaceffor imparting movement from the torque shaft to the control surface, a pair of variable speed power units, a differential gear coupling the power units to the torque shaft, connections between the pilots control member and the power units for initiating, on movement of the pilots. control member, operation of the power units to drive the torque shaft in a direction and at a rate determined by the direction and rate of movement of the control member, a follow-up gear connecting the differential gear and the power units for terminating operation of the power units when the control surface has assumed a position determined by the position of the con trol member, and means for preventing reverse rotation of either power unit, should it fail, by the other power unit.

file of this patent:

UNITED STATES PATENTS Number Name Date HENRY KNOWLER- 1,076,416 Gammeter 001;. 21, 1913 FRANK HENRY ROBERTSON 2,222,886 Voigt Nov126,1940 5 2,295,306 Tampier Sept. 8, 1942 REFERENCES CITED 2,406,374 Holt Aug. 27, 194 6 The following references are of record in the 2,412,027 Alexanderson Dec. 3, 1946 

